<?php
declare(strict_types=1);

class ApcuCacheTool implements \Psr\SimpleCache\CacheInterface
{
    /** @var string */
    private $prefix;

    /**
     * @param string $prefix
     */
    public function __construct(string $prefix)
    {
        $this->prefix = $prefix;
    }

    /**
     * Fetches a value from the cache.
     *
     * @param string $key     The unique key of this item in the cache.
     * @param mixed  $default Default value to return if the key does not exist.
     *
     * @return mixed The value of the item from the cache, or $default in case of cache miss.
     *
     * @throws \Psr\SimpleCache\InvalidArgumentException
     *   MUST be thrown if the $key string is not a legal value.
     */
    public function get(string $key, mixed $default = null): mixed
    {
        $value = \apcu_fetch("$this->prefix:$key", $success);
        if ($success) {
            return $value;
        }
        return $default;
    }

    /**
     * Persists data in the cache, uniquely referenced by a key with an optional expiration TTL time.
     *
     * @param string                 $key   The key of the item to store.
     * @param mixed                  $value The value of the item to store, must be serializable.
     * @param null|int|\DateInterval $ttl   Optional. The TTL value of this item. If no value is sent and
     *                                      the driver supports TTL then the library may set a default value
     *                                      for it or let the driver take care of that.
     *
     * @return bool True on success and false on failure.
     *
     * @throws \Psr\SimpleCache\InvalidArgumentException
     *   MUST be thrown if the $key string is not a legal value.
     */
    public function set(string $key, mixed $value, null|int|\DateInterval $ttl = null): bool
    {
        return \apcu_store("$this->prefix:$key", $value, $this->tllToInt($ttl));
    }

    /**
     * Delete an item from the cache by its unique key.
     *
     * @param string $key The unique cache key of the item to delete.
     *
     * @return bool True if the item was successfully removed. False if there was an error.
     *
     * @throws \Psr\SimpleCache\InvalidArgumentException
     *   MUST be thrown if the $key string is not a legal value.
     */
    public function delete(string $key): bool
    {
        return \apcu_delete("$this->prefix:$key");
    }

    /**
     * Wipes clean the entire cache's keys.
     *
     * @return bool True on success and false on failure.
     */
    public function clear(): bool
    {
        $iterator = new APCUIterator(
            '/^' . preg_quote($this->prefix . ':', '/') . '/',
            APC_ITER_NONE
        );
        return \apcu_delete($iterator);
    }

    /**
     * Obtains multiple cache items by their unique keys.
     *
     * @param iterable $keys    A list of keys that can obtained in a single operation.
     * @param mixed    $default Default value to return for keys that do not exist.
     *
     * @return iterable A list of key => value pairs. Cache keys that do not exist or are stale will have $default as value.
     *
     * @throws \Psr\SimpleCache\InvalidArgumentException
     *   MUST be thrown if $keys is neither an array nor a Traversable,
     *   or if any of the $keys are not a legal value.
     */
    public function getMultiple(iterable $keys, mixed $default = null): iterable
    {
        $keysToFetch = $this->keysToFetch($keys);
        $values = \apcu_fetch($keysToFetch);
        foreach ($keysToFetch as $keyToFetch) {
            if (!isset($values[$keyToFetch])) {
                $values[$keyToFetch] = $default;
            }
        }
        return $values;
    }

    /**
     * Persists a set of key => value pairs in the cache, with an optional TTL.
     *
     * @param iterable               $values A list of key => value pairs for a multiple-set operation.
     * @param null|int|\DateInterval $ttl    Optional. The TTL value of this item. If no value is sent and
     *                                       the driver supports TTL then the library may set a default value
     *                                       for it or let the driver take care of that.
     *
     * @return bool True on success and false on failure.
     *
     * @throws \Psr\SimpleCache\InvalidArgumentException
     *   MUST be thrown if $values is neither an array nor a Traversable,
     *   or if any of the $values are not a legal value.
     */
    public function setMultiple(iterable $values, null|int|\DateInterval $ttl = null): bool
    {
        $dataToSave = [];
        foreach ($values as $key => $value) {
            $dataToSave["$this->prefix:$key"] = $value;
        }
        return \apcu_store($dataToSave, null, $this->tllToInt($ttl));
    }

    /**
     * Deletes multiple cache items in a single operation.
     *
     * @param iterable $keys A list of string-based keys to be deleted.
     *
     * @return bool True if the items were successfully removed. False if there was an error.
     *
     * @throws \Psr\SimpleCache\InvalidArgumentException
     *   MUST be thrown if $keys is neither an array nor a Traversable,
     *   or if any of the $keys are not a legal value.
     */
    public function deleteMultiple(iterable $keys): bool
    {
        $keysToDelete = $this->keysToFetch($keys);
        return \apcu_delete($keysToDelete);
    }

    /**
     * Determines whether an item is present in the cache.
     *
     * NOTE: It is recommended that has() is only to be used for cache warming type purposes
     * and not to be used within your live applications operations for get/set, as this method
     * is subject to a race condition where your has() will return true and immediately after,
     * another script can remove it making the state of your app out of date.
     *
     * @param string $key The cache item key.
     *
     * @return bool
     *
     * @throws \Psr\SimpleCache\InvalidArgumentException
     *   MUST be thrown if the $key string is not a legal value.
     */
    public function has(string $key): bool
    {
        return \apcu_exists("$this->prefix:$key");
    }

    /**
     * @param iterable $keys
     * @return array
     */
    private function keysToFetch(iterable $keys): array
    {
        $keysToFetch = [];
        foreach ($keys as $key) {
            $keysToFetch[] = "$this->prefix:$key";
        }
        return $keysToFetch;
    }

    /**
     * @param null|int|\DateInterval $ttl
     * @return int
     */
    private function tllToInt(null|int|\DateInterval $ttl = null): int
    {
        if ($ttl === null) {
            return 0;
        } elseif (is_int($ttl)) {
            return $ttl;
        } elseif ($ttl instanceof \DateInterval) {
            return $ttl->days * 86400 + $ttl->h * 3600 + $ttl->i * 60 + $ttl->s;
        } else {
            throw new \Psr\SimpleCache\InvalidArgumentException("Invalid ttl value '$ttl' provided.");
        }
    }
}